How does Alice convince Bob that she possesses a particular credential
from Charlie? If Alice has a signature from Charlie on her public
key, then all she will need to do is to show this signature to Bob,
and also convince Bob that she is indeed Alice. How does Alice do
this without revealing her identity to Bob, or indeed any identifying
information? She produces a zero-knowledge proof of knowledge of the
requisite values rather than showing them in the clear. Research on
anonymous credentials, pioneered by David Chaum, concerns itself with
protocols that enable Alice to obtain and demonstrate possession of
credentials without revealing unnecessary information. Anonymous
delegation is a research area that concerns itself with the next
question: how does Alice delegate her credential to Bob without
revealing any information about herself and learning anything about
Bob? In this talk, I will survey what we know so far about anonymous
credentials and anonymous delegation.

This talk will be based on joint work with Mira Belenkiy, Jan
Camenisch, Melissa Chase, Markulf Kohlweiss and Hovav Shacham.

Speaker's Short Bio:

Anna Lysyanskaya is an Associate Professor of Computer
Science at Brown University. She received an A.B. in Computer Science
and Mathematics from Smith College in 1997, and a Ph.D. in Computer
Science and Electrical Engineering from MIT in 2002. She is a
recipient of an NSF CAREER award and a Sloan Foundation fellowship and
was included in the Technology Review Magazine's list of 35 innovators
under 35 for 2007. Her research interests are in cryptography,
theoretical computer science, and computer security.

Thursday, March 19: Prof. Amit Sahai, UCLA:
A New Paradigm for Secure Protocols.

Abstract:

One of the most fundamental goals in cryptography is to design
protocols that remain secure when adversarial participants can engage
in arbitrary malicious behavior. In 1986, Goldreich, Micali, and
Wigderson presented a powerful paradigm for designing such protocols:
their approach reduced the task of designing secure protocols to
designing protocols that only guarantee security against
"honest-but-curious" participants. By making use of zero-knowledge
proofs, the GMW paradigm enforces honest behavior without compromising
secrecy. Over the past two decades, this approach has been the
dominant paradigm for cryptographic protocol design.
In this talk, we present a new general paradigm for secure protocol
design. Our approach also reduces the task of designing secure
protocols to designing protocols that only guarantee security against
honest-but-curious participants. However, our approach avoids the use
of zero-knowledge proofs, and instead makes use of multi-party
protocols in a much simpler setting - where the majority of
participants are completely honest (such multi-party protocols can
exist without requiring any computational assumptions). Our paradigm
yields protocols that rely on Oblivious Transfer (OT) as a building
block. This offers a number of advantages in generality and
efficiency.
In contrast to the GMW paradigm, by avoiding the use of zero-knowledge
proofs, our paradigm is able to treat all of its building blocks as
"black boxes". This allows us to improve over previous results in the
area of secure computation. In particular, we obtain:

Conceptually simpler and more efficient ways for basing
unconditionally secure cryptography on OT.

More efficient protocols for generating a large number of OTs
using a small number of OTs.

Secure and efficient protocols which only make a black-box use of
cryptographic primitives or underlying algebraic structures in
settings where no such protocols were known before.

This talk is based on joint works with Yuvali Ishai (Technion and
UCLA) and Manoj Prabhakaran (UIUC).

Speaker's Short Bio:

Professor Amit Sahai received his Ph.D. in Computer Science from MIT
in 2000. From 2000 to 2004, he was a professor at Princeton
University; in 2004 he joined UCLA as an Associate Professor of
Computer Science, and as Associate Director of the Center for
Information and Computation Security. His research interests are in
security and cryptography, and theoretical computer science more
broadly. He has published more than 75 original technical research
papers at venues such as the ACM Symposium on Theory of Computing
(STOC), CRYPTO, and the Journal of the ACM. He has given a number of
invited talks at institutions such as MIT, Stanford, and Berkeley,
including the 2004 Distinguished Cryptographer Lecture Series at NTT
Labs, Japan. Professor Sahai is the recipient of numerous honors; he
was named an Alfred P. Sloan Foundation Research Fellow in 2002, and
received an Okawa Research Award in 2007. His research has been
covered by several news agencies including the BBC World Service.